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Patented a... 3, 1933 UNITED STATES PATENT OFFICE mom molds BOOTH, (HI-IBERIA G. TOBBEY, AND MZENAHEH HERLUB-SOBEI; OI

HEIGHTS, OHIO IEIHOIO non. m ELECTROLYTIC DEPOSITION OI mm Io Drawing.

This invention in one of its aspects, relates to a method for the electrodeposition of certain metals, which cannot be electrodeposited from aqueous solutions, as .well as metals, which though it is possible to electrolyticall deposit them from aqueous solutions, suc method is not satisfactory because it results in low current efliciencies and considerable hydrogen is released at the cathode simultaneously with the deposition of metal, which adverse]? afiects the character of the deposit and res ts in high commercial cost of operation.

In another aspect of the invention it relates to a method for the electrodeposition of metals other than those in the class prescribed above, wherein the electrol ic deposition is carried on in a solution 6 an appropriate salt of the metal in liquid ammoma or substituted ammonias (inorganic-or organic or a mixture thereof) while maintaining the temperature of the solution above the boiling point of the ammonia, in other words at room temperatures, and raising the boiling point of the ammonia by conducting the electrolytic operation under ressure, or by the addition tothe solution 0? a suitable substance or substances, the efiect of which will be to raise the boilin point of the solution.

A still urther aspect of the invention relates to the electrodeposition of metals of the class above rescribed, and in addition, other metals outside of the prescribed classes, in which there is dissolved in the liquid ammonia or substituted ammonias (as above referred to), a cyanide compound of the metal which is to be electrolytically deposited, such as cyanides, cyanate and thiocyanate.

We have found that by the use of appropriate salts dissolved in liquid ammonia or. [substituted ammonias, (inorganic or organic oramixture thereof) it is possible to obtain electrodeposition of metals, which are-not at all obtainable from water solution, and on the other hand, to obtain a more efficient, as well as better deposition of metals, which are capable of electrolytic. deposition from water solution. We have found that compact adherent metal deposits are quite feasible from liquid ammonia solution (and its sub- Application fled June as, iaao. Serial No. 404,104.

stituted compound) by the use of proper voltage and current density, both at low temperatures while maintaining the liquid bath under pressure to control the boiling point of the liquid ammonia, or at artificially maintained higher temperatures and under normal pressure conditions.

We have found that metals electrode osited from solution of ammonia or substltuted ammonias, possess unusual corrosion resisting characteristics, probably due to the favorab e conditions under which deposition has taken place.

As an example of one a plication of the present invention, we woul refer to the electrodeposition of beryllium, which metal, so

far as we are aware, has never before been electrolytically deposited from any solvent, and, so far as we are aware, is obtainable only b the use of fused electrolytes. For examp e, theiodide of beryllium. may be dissolved in ammonia at about the boiling point of the solvent, and upon electrolyiis there will be obtained a deposition of, ryllium on the cathode. Chloride of beryllium may be used equally well, although with the last named solute, it is preferable to operate while maintaining suitable pressure within the electrolytic cell at normal tem ratures. The higher temperature obtaina le under pressure, gives the beryllium chloride greater solubility.

While reference has here been made to the use of liquid ammonia, it will be understood that substituted ammonias will also act as a solvent and give the desired deposition of beryllium, (even as complex a substituted unit as piperidine gives positive results). The use of liquid ammonia as a solvent is preferred largely on account of lower cost.

In addition to the use of pressure, in order to raise the boiling point of the liquid ammonia, we have foundit feasible to obtain the same effect by the addition of certain salts to the liquid ammonia, as examples of which we may cite ammonium thiocyanate and the like, or certain inert materials which are.

soluble in liquid ammonia, as an example of which we may mention sugar, which because of their great solubility raise the boiling point trclytic action, using about twelve to fifteen the electrolytic deposition of beryllium, either at the boiling oint of ammonia or at room temperatures as before explained).

Without in any way intending to limit the scope of the present invention, we would give one or two examples of the operation of the foregoing invention.

Anhydrous beryllium iodide-may be dissolved in liquid ammonia about six grams of a salt to every one hundred cubic centimeters of the solvent at the normal boiling point of ammonia. This solvent is subjected to ele amperes per square decimeter of cathode area. The voltage necessarv will vary with the efiectiveness of the stirring of the solution, and will also be afiected whether or not a beryllium anode is used. The cathodic current density is by no means critical. A very satisfactory deposition of metallic beryllium was thus obtained.

As another example we would state that a satisfactory deposition of beryllium was obtained from a saturated solution of beryllium chloride in liquid ammonia (temperature of the bath approximately 38 C.) using a current density 'of 2.5 amperes per square decimeter and a line voltage of 10 volts. As illustrating a variation of both current density and voltage, with a solution as above mentioned, aperhaps more satisfactory deposit was obtained by using a current density of 0.6 amperes per square decimeter and a line voltage of 4 volts.

As another example of the electrolytic disposition of metals which cannot be deposited from aqueous solutions, we would cite the case of boron. A solution of a halide of boron in liquid ammonia (at either low or high temperatures and pressures) will. upon electrolysis of the solution, deposit metallic boron at the cathode.

- Manganese may be cited as an example of a class of metalswhich can be electrolytically .deposited to some extent. from-aqueous solution, but gives considerable difliculty of one kind or another. Salts of this metal when electrolyticallydeposited in a water solution, glve a small amount of deposition, but the deposit soon deteriorates upon continued electrolytic action. Moreover, there is a great tendency for the metal to ,oxidize, in the same manner as iron will rust.

On the other hand, using manganese salts, as for instance, manganese thiocyanate, disaeeaam er purity and will withstand deterioration in corrosive atmosphere for a long period of time.

As a practical example of the electrolytic deposition of manganese, we would state that good deposition yield has been obtained byv using about one gram of manganese thiocyanate for every one hundred cubic centimeters of liquid ammonia (at the boiling point of ammonia). The current densit must be regulated to the concentration 0 the salt, but when the concentration, as given above, is used, a current density of about two-tenths amperes per square decimeter of cathode surface gives good results. If metallic manganese is used as an anode, the corrosion of the above is almost perfect.

Chromium is also a metal which can be deposited from liquid ammonia solution, much more satisfactorily than it can be deposited from'a solution of chromium salts in water. By the use of chromic thiocyanate (the violet form is preferable over the green form because ofsolubility, although the green orm turns to the violet form on contact with arm-- mania) chromium can be deposited uponthe cathode electrolytically with far better throwing power than any aqueous solutions, with which we are conversant.

Since oor throwing power is one of the outstanding difiicultiesin present day chromimn plating practice, electrolytic deposition from liquid ammonia solutions presents great advantages over the usual chromium plating practices at present in use.

We would further point out that many metals, though giving relatively high current efficiencies when electrolytically deposited in a water solution, can better be deposited from liquid ammonia solution at temperatures higher than the boiling point, but not at the low temperature of the boiling point of ammonia.

We have found that many of the obstacles inherent in low temperature electrolysis, are automatically eliminated in raising the temperature of operation to the normal, either by pressure or by the presence of a material in the solution, the result of which is to raise the boiling point thereof.

When using pressure, besides the temperature factor itself, and-its corrolary increase in the solubility of salts, there is one additional factor of importance to be considered,,

to-wit, that the increase in pressure acts to 1 case of those metals higher in the electromotive series than the hydrogen itself.

Without intending any limitation, we would state that we have found that the best deposition occurs Where the metal salts used are cyanides or cyanide addition compounds, such as cyanates, thiocyanates and similar compounds.

, Where in the claims the word ammonia is used without qualification, we intend that it shall be taken as a generic term, including liquid ammonia as Well as substituted ammonias, either inorganic or organic, Also inthe claims where the term cyanide compound is used it is intended to be generic, and to include not only cyanides, but cyanide addition compounds, such as cyanate and thiocyanate.

It will be understood that various deviations may be made from the disclosure of the invention heretofore given, without departing from the spirit of the invention, and such deviations are considered to be Within the purview of the present invention.

Having thus described our invention what We claim is:

1. The method for electrodeposition of beryllium which consists in electrolyzing a solution of a salt of beryllium in ammonia.

2. The method for electrodeposition of beryllium which consists in electrolyzing a solution of a salt of berryllium in liquid ammonia.

3. The method of electrodeposition of beryllium which consists in electrolyzing a solution of a salt of beryllium in liquid ammonia and adding to the solution ammoniasoluble materials to raise the normal boiling point of the liquid ammonia, the tem- 40 perature of the solution being above the normal boiling point of the liquid ammonia.

4. The method of electrodeposition of beryllium which consists in electrolyzing a solution of a salt of beryllium in liquid ammonia, the said solution being maintained under pressure greater than atmosphere and the temperature of the solution being above the normal boiling point of the liquid ammonia.

In testimony whereof, we hereunto affix our signatures.

HAROLD SIMMONS BOOTH. GILBERTA G. TORREY MENAHEM MERLUB-SOBEL 

